The present invention relates to polyamide compositions and in particular to copper-stabilized polyamide 4.6 compositions. The use of copper compounds, in particular copper salts, such as copper halides, as a stabilizer of polyamides is known. JP-A-86-289660 points out the particular effect of the presence of potassium iodide in addition to the copper salt, copper iodide, giving very good thermal stability of polyamide 4.6 for a very long time. The use of copper iodide alone only provides a marginal improvement of the thermal stability. In the case of polyamide 4.6 used in for instance in electric and electronic equipment, however, the presence of free potassium iodide is prohibited because of the high risk of corrosion and frequently too high electrical conductivity of the material.
The most obvious solution for stabilizers of polyamide 4.6 compositions in electrical/ electronic applications consequently lies in the use of non-ionic organic compounds having a stabilizing effect.
However, an extensive examination of the commercially available stabilizers and stabilizer combinations did not yield an organic non-ionic stabilizer meeting the high stability requirements at the elevated temperatures that are necessary for many electronic/electric applications.
Very surprising, it is now found that a combination of a water insoluble copper salt in a very low concentration with a halogen-substituted organic compound has an unexpectedly strong stabilizing effect in polyamide 4.6 compositions.